Cool–Warm Temperature Stratification and Simulated Bird Digestion Optimize Removal of Dormancy in Rosa rugosa Seeds

Rosa rugosa Thunb. has been explored multi-function in medicinal, edible, cosmetic, ornamental and ecological etc. However, R. rugosa natural populations have recently declined substantially in China, besides of global climate change, this species also has the defect of limiting the reproduction of itself such as the hard-to-release seed dormancy. In this study, only 30% of R. rugosa seeds were viable, and the others were incompletely developed or diseased seeds. Without stratification, morphologically complete viable seeds imbibed water but those seeds could not germinate even after seed husk removal under suitable condition to exhibit a physiological dormancy. After cold (4°C) and warm (18 ± 2°C) stratification, macromolecular substances containing carbon or nitrogen accumulated, and respiration, antioxidant enzyme activity, and gibberellin (GA3) /abscisic acid (ABA) and auxin (IAA)/ABA ratios increased significantly in seeds. Water absorption also increased as endocarps softened. Thus, physiological dormancy of seed was broken. Although warm and cold stratification increased separation between endocarp and embryo, the endocarp binding force was removed insufficiently, because only 10.20% of seeds germinated. Therefore, stratified seeds were treated with simulated bird digestion. Then, folds and cracks in loosened endocarps increased permeability, and water absorption rate increased to 64.43% compare to 21.14% in cold and warm stratification treatment. With simulated digestion, 24.20% of radicles broke through the endocarp with plumules and cambiums to develop into seedlings. Thus, the seed dormancy type of R. rugosa is physiological as seeds imbibed water and possessed fully developed embryos with a low growth potential in combination with a mechanical constraint from the endocarp. Cold stratification helped remove physiological dormancy, and additional warm stratification accelerated the process. The optimal stratification treatment was 4°C for 45 days followed by 18 ± 2°C for 15 days. After warm and cold stratification, simulated bird digestion broke the mechanical constraint from the seed covering layers. Based on this research, production of R. rugosa seedlings can be greatly increased to help protect the species from further declines.

Growth and development of representatives of the genus Rosa L. in the Stavropol Botanical Garden

Relevance. To identify the features of the growth and development of species of roses of different geographical origin, to establish the biological minimum temperatures necessary for the beginning of flowering of representatives of the genus Rosa L., to study the morphological indicators of fruits.Methodology. The research material was 12 wild roses belonging to 4 sections: Canina Crep, Cinnamomeae DC, Luteae Crep, Pimpinellifoliae DC. The research was carried out using the methods of the Main Botanical Garden, floral and geographical analyses — according to Hrzhanovsky. A caliper was used to measure the length and diameter of 10 fruits. For the analysis of statistical data, the MS Excel table processor and the integrated MATLAB mathematical package were used.Results. The article presents the results of a study of species of roses in the Stavropol Botanical Garden of various geographical origin. The study involved 12 species belonging to 4 sections. The features of growth and development of plants in new soil and climatic conditions are revealed. The dates of the beginning of the main phenological phases andtheir duration have been established: spring regrowth of shoots, budding, beginning and end of flowering, fruiting. In the studied species of roses, the growing season begins in the first — second decade of March, flowering occurs in late May — early June, the fruits ripen in August — September. The dependence of the timing of the beginning of flowering in the studied roses on the dynamics of the accumulated average daily air temperatures and the sum of effective temperatures above 5 °C was revealed. Mathematically, it was proved that the lower limit of the air temperature required for the beginning of flowering of species of roses is +16 °C, when the sum of the average daily temperature air St° = 1007.75–1069.48 °С and St эф > 5 °С = 530.75–594.75 °С are accumulated. Early flowering species of roses include Rosa foetida Herrm., R. pendulina L., R. pimpinellifolia L., late flowering — R. caudata Baker and R. corymbifera Borkh. The shortest flowering period is in R. caudata Baker, R. jacutica Juz. and R. kamtschatica Vent. Representatives of those types mostly bloom once. Their flowers are formed on biennial and more mature shoots. The flowering period is 13–23 days. Rosa rugosa Thunb. blooms again, its flowering period is extended and long — from 40 to 48 days. All species of roses form fruits. The longest fruits are in R. pendulina L., R. caudata Baker, R. rugosa Thunb., R. corymbifera Borkh. and R. canina L., and large ones — in R. rugosa Thunb., R. marretii Lev. and R. roxburghi Tratt.

Invasion at the Edge: The Case of Rosa rugosa (Rosaceae) in Italy

The Japanese Rose (Rosa rugosa) is a perennial shrub belonging to the family Rosaceae. It was introduced in Europe from East Asia as an ornamental plant in the XIX century and is now considered an invasive species, especially in northern Europe, colonising the Atlantic and Baltic coastal dune habitats and threatening local biodiversity. However, little is known about its presence and invasion patterns in the Mediterranean area. In Italy, R. rugosa has been classified as naturalised and just a few observations have been recorded in dune habitats in the North Adriatic coast. Here, we review the published data on R. rugosa in Europe and present preliminary data on the invasive pattern of R. rugosa on the Italian North Adriatic coast. We surveyed the coastline in two locations (i.e., Brussa and Bibione, Italy) where we characterised the dimension and structure (i.e., number of ramets and stem height) of the R. rugosa populations and listed the associated floristic composition. No occurrence of R. rugosa was recorded in Bibione, probably due to the success of the restoration project carried out on that site. In contrast, several stands of R. rugosa were found in Brussa, where many other alien species were also found (accounting for 15.28% of the sampled species). Given the strong invasiveness of R. rugosa, it is important to keep data on its distribution up-to-date and investigate its ecology and physiology to promote appropriate management strategies to control its spread and anticipate its future potential distribution.

Genome-Wide Identification of LATERAL ORGAN BOUNDARIES DOMAIN (LBD) Transcription Factors and Screening of Salt Stress Candidates of Rosa rugosa Thunb

LATERAL ORGAN BOUNDARIES DOMAIN (LBD) transcription factors are regulators of lateral organ morphogenesis, boundary establishment, and secondary metabolism in plants. The responsive role of LBD gene family in plant abiotic stress is emerging, whereas its salt stress responsive mechanism in Rosa spp. is still unclear. The wild plant of Rosa rugosa Thunb., which exhibits strong salt tolerance to stress, is an ideal material to explore the salt-responsive LBD genes. In our study, we identified 41 RrLBD genes based on the R. rugosa genome. According to phylogenetic analysis, all RrLBD genes were categorized into Classes I and II with conserved domains and motifs. The cis-acting element prediction revealed that the promoter regions of most RrLBD genes contain defense and stress responsiveness and plant hormone response elements. Gene expression patterns under salt stress indicated that RrLBD12c, RrLBD25, RrLBD39, and RrLBD40 may be potential regulators of salt stress signaling. Our analysis provides useful information on the evolution and development of RrLBD gene family and indicates that the candidate RrLBD genes are involved in salt stress signaling, laying a foundation for the exploration of the mechanism of LBD genes in regulating abiotic stress.

A high-quality chromosome-level genome of wild Rosa rugosa

Rosa rugosa is an important shrub with economic, ecological, and pharmaceutical value. A high-quality chromosome-scale genome for R. rugosa sequences was assembled using PacBio and Hi-C technologies. The final assembly genome sequences size was about 407.1 Mb, the contig N50 size was 2.85 Mb, and the scaffold N50 size was 56.6 Mb. More than 98% of the assembled genome sequences were anchored to seven pseudochromosomes (402.9 Mb). The genome contained 37,512 protein-coding genes, with 37,016 genes (98.68%) that were functionally annotated, and 206.67 Mb (50.76%) of the assembled sequences are repetitive sequences. Phylogenetic analyses indicated that R. rugosa diverged from Rosa chinensis ∼6.6 million years ago, and no lineage-specific whole-genome duplication event occurred after divergence from R. chinensis. Chromosome synteny analysis demonstrated highly conserved synteny between R. rugosa and R. chinensis, between R. rugosa and Prunus persica as well. Comparative genome and transcriptome analysis revealed genes related to colour, scent, and environment adaptation. The chromosome-level reference genome provides important genomic resources for molecular-assisted breeding and horticultural comparative genomics research.